1. Field of the Invention
The present invention relates to a probe apparatus for measuring electric characteristics of an object such as a semiconductor wafer.
2. Description of the Related Art
In a process of manufacturing semiconductor devices, a number of semiconductor devices are formed on a semiconductor wafer using a precision photograph transfer technology, and the wafer is diced to separate the semiconductor devices from one another. In this process, the electric characteristics of semi-finished semiconductor devices are measured using a probe apparatus when they are formed on the semiconductor wafer, and only defect-free devices of the semi-finished semiconductor devices are sent to the succeeding process such as a packaging process, thereby improving productivity of the semiconductor devices.
The probe apparatus includes a wafer holding table movably in the X, Y and Z directions. A probe card having a number of probes corresponding to electrode pads of the semiconductor devices is fixed onto the wafer supporting table. The semiconductor wafer is placed on the wafer supporting table, and the wafer supporting table is driven to bring the probes into contact with the electrode pads of the semiconductor devices, thereby testing the semiconductor devices using a tester and measuring their characteristics by the probes.
Since a miniaturized circuit pattern has to be formed in the semiconductor device manufacturing process described above, dust in an atmosphere adheres to the semiconductor wafer and causes defective semiconductor devices. For this reason, the semiconductor devices are usually manufactured in a clean room in which a downflow of clean air is generated. The probe apparatus is installed in the clean room and the characteristics of the semiconductor devices are measured.
Since, however, the construction cost of a clean room is high per floor area, it is desirable that the number of apparatuses installed in the clean room be as few as possible. Further, since people tend to generate dust, it is desirable that as few operators as possible enter the clean room.
Usually, the surface of the electrode pad of the semiconductor device comes into contact with air to form an oxide film thereon. The distal end of the each probe of the probe apparatus slides along the surface of the electrode pad, and the oxide film is removed by the distal end of the probe, with the result that the electrode pad and the probe are brought into electrical contact with each other. However, the following problem will arise. There is a strong possibility that the removed oxide floats as dust and adheres to an undesired portion. To eliminate this problem, a technique of preventing the adhesion of dust by forming a downflow of air in a region for mounting the semiconductor wafer is proposed in Published Unexamined Japanese Patent Application No. 63-151036. Even though this technique is adopted, an effect of preventing the adhesion of dust cannot be sufficiently obtained.